Search results for "Neutron diffraction"
showing 10 items of 102 documents
X-ray absorption spectroscopy study of local dynamics and thermal expansion in ReO3
2015
The thermal expansion of polycrystalline ${\mathrm{ReO}}_{3}$ is studied in vacuum by x-ray diffraction from 300 to 600 K and by extended x-ray absorption fine structure (EXAFS) at the Re ${L}_{3}$ edge from 30 to 600 K. A detailed EXAFS analysis is presented up to the sixth coordination shell around Re. The crystal thermal expansion is weak throughout the explored range, negative below 100 K, positive from 150 to 500 K, and negative again above 500 K. The analysis of mean square relative displacements obtained by EXAFS and of mean square displacements available from x-ray and neutron diffraction measurements confirms the presence of significant static disorder in the investigated samples. …
Brain lateralization probed by water diffusion at the atomic to micrometric scale
2019
International audience; Combined neutron scattering and diffusion nuclear magnetic resonance experiments have been used to reveal significant interregional asymmetries (lateralization) in bovine brain hemispheres in terms of myelin arrangement and water dynamics at micron to atomic scales. Thicker myelin sheaths were found in the left hemisphere using neutron diffraction. 4.7 T dMRI and quasi-elastic neutron experiments highlighted significant differences in the properties of water dynamics in the two hemispheres. The results were interpreted in terms of hemisphere-dependent cellular composition (number of neurons, cell distribution, etc.) as well as specificity of neurological functions (s…
Material quality characterization of CdZnTe substrates for HgCdTe epitaxy
2006
Cd1−xZnxTe (CZT) substrates were studied to investigate their bulk and surface properties. Imperfections in CZT substrates affect the quality of Hg1−xCdxTe (MCT) epilayers deposited on them and play a role in limiting the performance of infrared (IR) focal plane arrays. CZT wafers were studied to investigate their bulk and surface properties. Transmission and surface x-ray diffraction techniques, utilizing both a conventional closed-tube x-ray source as well as a synchrotron radiation source, and IR transmission micro-spectroscopy, were used for bulk and surface investigation. Synchrotron radiation offers the capability to combine good spatial resolution and shorter exposure times than conv…
Determination of the conformation of polymers in the amorphous solid state and in concentrated solution by neutron diffraction
1975
Abstract From the coherent neutron scattering on dilute solid solutions of the ordinary polymer within the deuterated polymer, conformation parameters of polymer chains in amorphous solid states can be determined. In this way vitreous poly(methyl methacrylate) (PMMA) has been investigated. The chains form unperturbed coils and the radius of gyration is very near to the corresponding value in dilute solutions of the same polymer in the low molecular θ-solvent butyl chloride. The same principle of measurement has been applied to concentrated solutions of PMMA in D-acetone. The solutions contained 50% polymer, the main part of which (98% and more) was deuterated so that the system was opticall…
Phases and phase transitions in the mixed molecular system (NaCN)1x(KCN)x
1990
The phase diagram of (NaCN)1−x(KCN)x was examined by neutron powder diffraction in the temperature range 5K ≦T≦300 K. Several non-cubic low-temperature phases were identified for concentrationsx<xc1=0.15 andx≧xc2=0.89. Lattice parameters and ferroelastic deformations were determined from the observed powder patterns. The phase transformations were characterized following the temperature dependence of the appropriate order parameters.
Contributions to the application of the transferability principle and the multipolar modeling of H atoms: electron-density study of L-histidinium dih…
2006
The electron density of L-histidinium dihydrogen orthophosphate orthophosphoric acid has been determined from X-ray and neutron diffraction data at low temperature (120 K). Topological analysis of the electron density has been used to analyse the effect of the multipolar refinement strategy on the electron-density model in the hydrogen-bonding regions. The electron density at low temperature has also been used to acquire high-quality experimental thermal parameters at room temperature using the transferability principle. Molecular vibrations, TLS and normal mode analysis are discussed and studied at both temperatures.
Temperature dependence of the static structure factor of ortho-terphenyl in the supercooled liquid regime close to the glass transition
1993
Abstract Studying the temperature dependence of the static structure factor of ortho-terphenyl from the liquid state down to the glass we find that the main peak of S ( Q ) is split into two maxima which behave quite differently. While the maximum at Q =1.4 A −1 is not much affected by the temperature variation the one at 1.9 A −1 is significantly enhanced. This effect is connected with a change of the short range order, i.e. of the intermolecular distances, but evolves continuously. Thus the dynamic anomalies that have been observed in this system around a characteristic temperature T c ≈290 K are not simply due to a discontinuous change in S ( Q ) but can be attributed to the existence of…
A neutron diffraction study of the glass transition in (KBr)0.47(KCN)0.53
1985
Abstract The molecular crystal (KBr) 0.47 (KCN) 0.53 has been investigated by elastic neutron diffraction at the transition from the paraelastic to the orientational glass state. The freezing temperature is characterized by the onset of a momentum transfer dependent broadening of the diffraction lines indicating the transition from a crystalline to an amorphous state.
Hydration dependence of myoglobin dynamics studied with elastic neutron scattering, differential scanning calorimetry and broadband dielectric spectr…
2014
In this work we present a thorough investigation of the hydration dependence of myoglobin dynamics. The study is performed on D2O-hydrated protein powders in the hydration range 0<h<0.5 (h≡gr[D2O]/gr[protein]) and in the temperature range 20-300K. The protein equilibrium fluctuations are investigated with Elastic Neutron Scattering using the spectrometer IN13 at ILL (Grenoble), while the relaxations of the protein + hydration water system are investigated with Broadband Dielectric Spectroscopy; finally, Differential Scanning Calorimetry is used to obtain a thermodynamic description of the system. The effect of increasing hydration is to speed up the relaxations of the myoglobin + hydration …
Experimental evidence for a liquid-liquid crossover in deeply cooled confined water.
2014
International audience; In this work we investigate, by means of elastic neutron scattering, the pressure dependence of mean square displacements (MSD) of hydrogen atoms of deeply cooled water confined in the pores of a three-dimensional disordered SiO 2 xerogel; experiments have been performed at 250 and 210 K from atmospheric pressure to 1200 bar. The " pressure anomaly " of supercooled water (i.e., a mean square displacement increase with increasing pressure) is observed in our sample at both temperatures; however, contrary to previous simulation results and to the experimental trend observed in bulk water, the pressure effect is smaller at lower (210 K) than at higher (250 K) temperatur…